One persistent problem I've found with Sparky after first installation - and I've installed it on several machines now - is that after having set it up it's very easy not to realise that it's launched with Number Lock engaged.
This means of course that your password won't be recognised because you are, unbeknownst to yourself, failing to type in the correct alphanumeric combination.
This makes for a very frustrating and trying time until the penny finally drops!
You're lucky ;D I can try to get the numlock on without any result (also setting it in the settings)
What is your desktop environment ?
I guess simplest way to fix your issues would be to install numlockx and add to your session autostart numlockx off to disable NumLock at boot.
By analogy same tool can be used to enable NumLock at boot with numlockx on